The present invention relates to an electric discharge lamp apparatus having a structure that a metal lead support arranged to support the leading end of an arc tube and serving as a passage for supplying electric power to an arc tube projects over an insulating plug thereof.
As shown in FIG. 17, a conventional electric discharge lamp apparatus has a structure that an arc tube 5 is integrally secured at a position in front of an insulating plug, i.e. an insulating base 1 made of synthetic resin.
The arc tube 5 has a structure that an ultraviolet-ray shielding globe 9 is integrally welded to an arc tube body 6 having an enclosed glass bulb 7 which is a light emitting portion in which electrodes 7a and 7b are disposed opposite to each other. Thus, the enclosed glass bulb 7 is surrounded and sealed by the ultraviolet-ray shielding globe 9. The electrodes 7a and 7b are connected to lead wires 8c and 8d extending from the arc tube 5 through molybdenum foil portions 8a and 8b bonded to pinch seal portions 8.
The rear end of the arc tube 5 is inserted into an engaging hole la formed in the insulating plug 1. The rear outer surface of the disc 2 is held by a dish-shape disc 2 made of ceramics and secured to the front surface of the insulating plug 1 with screws. Moreover, the leading end of the arc tube 5 is supported by a metal lead support 3 forwards projecting over the insulating plug 1 and serving as a passage for supplying electric power to the arc tube 5. Thus, the arc tube 5 is integrally secured to the insulating plug 1. Reference numeral 2a represents bond with which the inside portion of the disc 2 is filled. A ceramic insulating sleeve 4 is arranged to maintain insulation between the positive-side electric-power passages 8d, 8b and 7b and the metal lead support 3 which is a negative-side electric-power passage, the insulating sleeve 4 being formed into a cylindrical pipe shape disposed to cover the metal lead support 3.
The above-mentioned conventional electric discharge lamp apparatus has the structure that the insulating sleeve 4 covers the metal lead support 3. When the electric discharge lamp apparatus is assembled, the metal lead support 3 must be inserted into the ceramic sleeve 4. To smoothly insert the lead support 3 into the sleeve 4, the inner diameter of the sleeve 4 must be larger than the outer diameter of the lead support 3. However, if the inner diameter of the sleeve 4 is enlarged a gap is formed from the inserted lead support 3. As a result, the two elements 3 and 4 are relatively moved, causing noise to be made. Moreover, there is apprehension that the sleeve 4 is broken. Therefore, the conventional structure has been arranged to smoothly perform the process for inserting the lead support and prevent noise and breakage of the sleeve by making the inner diameter of the sleeve 4 to be slightly larger than the outer diameter of the lead support 3.
The insulating sleeve 4 is molded by sintering. Since the volume is reduced after the insulating sleeve 4 has been sintered, it is difficult to accurately control the dimension accuracy of the sleeve 4 (the inner and outer diameters and the straightness). Therefore, the manufacturing yield of the molded sleeve 4 is unsatisfactory and thus the cost of the electric discharge lamp apparatus is enlarged excessively.
To solve the above-mentioned problems experienced with the conventional technique, an object of the present invention is to provide an electric discharge lamp apparatus with which satisfactory workability is realized when the electric discharge lamp apparatus is assembled, which is free from apprehension of noise and breakage of the sleeve and which enables cost to be reduced.
To achieve the above-mentioned object, according to a first aspect of the invention, there is provided an electric discharge lamp apparatus comprising: an arc tube; an insulating plug made of synthetic resin, the insulating plug supporting the arc tube; a metal lead support serving as a passage for electric power to be supplied to the arc tube, wherein the metal lead support has a bent portion; an insulating sleeve made of ceramics wherein the insulating sleeve has a hollow pipe shape and an inner surface into which the lead support is inserted, wherein a predetermined gap is provided between the inner surface of the insulating sleeve and an outer surface of the lead support, and the bent portion of the metal lead support comes contact with the inner surface of the insulating sleeve.
The gap between the inner surface of the insulating sleeve and the outer surface of the lead support has a size with which the bent portion of the lead support is brought into close contact with the inner surface of the insulating sleeve so that the lead support and the insulating sleeve are integrated with each other. Moreover, when the lead support is inserted into the insulating sleeve, the size enables the bent portion of the lead support to elastically be deformed to smoothly insert the lead support into the insulating sleeve.
Since the inner diameter of the insulating sleeve is larger than the outer diameter of the lead support and the bent portion can elastically be deformed along the insulating sleeve when the lead support is inserted into the sleeve, the lead support can smoothly be inserted into the insulating sleeve even if the inner diameter of the insulating sleeve has an error or the insulating sleeve is warped.
Since the lead support is pressed against the insulating sleeve at a plurality of positions in the lengthwise direction in the insulating sleeve, the insulating sleeve is integrated with the lead support. Therefore, the two elements are not relatively vibrated by dint of transmitted vibrations and thus looseness of the two elements can be prevented. As a result, the apprehension that the insulating sleeve is broken can be eliminated.
According to a second aspect of the invention, there is provided the electric discharge lamp apparatus of the first aspect, wherein the insulating plug has a sleeve insertion hole which is opened in the front surface of the insulating plug and through which the rear end of the insulating sleeve is inserted so as to be accommodated, and the predetermined gap is provided between the inner surface of the sleeve insertion hole and the outer surface of the insulating sleeve.
The insulating sleeve is disposed to also cover a region of the lead support extending into the insulating plug in addition to the portion forwards extending over the insulating plug. As a result, insulation between the positive-side electric-power passage and the negative-side electric-power passage disposed opposite to each other can be maintained.
The diameter of the sleeve insertion hole is larger than the outer diameter of the insulating sleeve. Therefore, even if the outer diameter of the insulating sleeve has an error or if the insulating sleeve is warped the insulating sleeve can smoothly be inserted into the sleeve insertion hole.
According to a third aspect of the invention, there is provided the electric discharge lamp apparatus of the second aspect, wherein the insluating plug has a lead-support insertion hole, and a tapered hole communicating between the sleeve insertion hole and the lead-support insertion hole.
The rear end of the lead support which has been pushed into the insulating sleeve and which has penetrated the insulating sleeve is moved along the tapered hole so as to be guided into the lead-support insertion hole.
According to a fourth aspect of the invention, there is provided the electric discharge lamp apparatus of the third aspect, wherein the lead-support insertion hole is eccentric with respect to the sleeve insertion hole, and the lead support which is inserted through the lead-support insertion hole and which is eccentric with respect to the sleeve insertion hole presses a side surface of the insulating sleeve against the inner surface of the sleeve insertion hole.
Since the lead support which is eccentric from the central axis of the sleeve insertion hole presses the overall region of a side surface of the inner surface of the insulating sleeve in the lengthwise direction, looseness of the insulating sleeve with respect to the sleeve insertion hole can be prevented.